Specific Features of the Magnetocaloric Effect in a Uniaxial Paramagnet with Kramers Ions

The changes in magnetic entropy upon isothermal magnetization of a uniaxial paramagnet with Kramers ions (spin S = 3/2) and single-ion easy-plane anisotropy were studied at low temperatures. It was demonstrated that the magnetocaloric effect upon magnetization in the easy direction is considerably stronger than the one corresponding to magnetization in the hard direction (perpendicular to the easy plane). It was found that magnetization in the hard direction is accompanied by an anomalous increase in magnetic entropy in a finite interval of magnetic fields. A nonmonotonic dependence of entropy on the final magnetization field is produced as a result.